DESCRIPTION

io_prep_pread is an inline convenience function designed to facilitate
the initialization of the iocb for an asynchronous read operation.
The first iocb->u.c.nbytes=count bytes of the file for which
iocb->aio_fildes=fd is a descriptor are written to the buffer
starting at iocb->u.c.buf=buf. Reading starts at the absolute
position ioc->u.c.offset=offset in the file.
This function returns immediately. To schedule the operation, the
function io_submit must be called.
Simultaneous asynchronous operations using the same iocb produce
undefined results.